In the field of photogrammetry, it is often needed to determine part edge in carrying out non-contact or non-destructive measurement of the part; and it is needed in picture search to extract the edge pixels of an image.
A measure method, that is to scan object cross-section layer by layer along one direction using computerized tomography, to obtain a series of slices is also called “cross-sectional measurement”. Through extracting the cross-sectional contour of the object by means of the cross-sectional images, 3D reverse and reconstruction of the object could be achieved. Through a picture obtained by industrial CT or the like, the contour of the sectional entity could be transfered into a STL file, which is commonly used in rapid prototyping system, to immediately obtain the 3D model; or the contour of the sectional entity could be transfered into codes for NC machining, to machine a 3D part directly. A critical step during this process is to extract entity edge from the picture.
It has been found after search that edge extractions previously were all based on a single pixel, such as in CN 1711559A (Seiko Epson Corp), wherein the accuracy was no higher than the pixel accuracy and the processing speed is low.